Controls for heat pumps having outdoor air coils



United States Patent 3,191,399 CONTROLS FOR HEAT PUMPS HAVING OUTDOORAIR COILS Robert S. Stewart, Staunton, Va., assiguor to WestinghouseElectric Corporation, Pittsburgh, Pa., a corpora tion of PennsylvaniaFiled Aug. 11, 1964, Ser. No. 388,853 1 Claim. (Cl. 62-160) Thisinvention relates to thermostatic controls for heat pumps used forcooling or heating indoor air.

A heat pump used for cooling or heating indoor air usually has an indoorcoil that operates as an evaporator when air cooling is required, and asa condenser when air heating is required, and has an outdoor coil thatoperates as a condenser when air cooling is required, and

as an evaporator when air heating is required.

When such a heat pump is operated to cool indoor air, at relatively lowoutdoor temperatures, the condensing pressure may be so low that thereis insufficient pressure at the refrigerant expansion means to operateit properly. My U.S. Patent 3,112,620 discloses how condensing pressurecan be increased when the outdoor temperature drops. Three fans are usedto cool the outdoor coil with outdoor air. On a predetermined drop inoutdoortemperature, one fan is turned oif. On a further drop in outdoortemperature, the other two fans are turned oil, and the one fan isturned back on. Only a single two-stage, outdoor thermostat and tworelays are required to operate three fans, two fans or one fan dependingon the outdoor temperature. This so-called low ambient control is widelyused.

When the heat pump'is used to heat indoor air, a low ambient control isnot required since the condenser is the indoor coil. fBut, a so-calledhigh ambient control is esirable .for controlling compressor headpressures. This invention adapts the low ambient control of my patent sothat it operates as a high ambient control during air heating operation,as well as a low ambient control during air cooling operation.

An object of this invention is to combine lowambient and high ambientcontrols of a heat pump.

Another object of this invention is to reduce the number of componentsrequired for low and high ambient controls of a heat pump.

This invention will now be described with reference to the annexeddrawings, of which:

FIG. 1 is a diagrammatic view of a heat pump embodying this invention;

FIG. 2a is a diagrammatic view of an outdoor thermostat used with theheat pump;

FIG. 2b is a diagrammatic view of a cooling relay used with the heatpump;

FIG. 20 is a diagrammatic view with the heat pump;

FIG. 2d is a diagrammatic view of a starter for the compressor motor ofthe heat pump;

FIG. 22 is a diagrammatic view of a starter for one of the three outdoorfans of the heat pump;

iFlG. 2f is a diagrammatic View of a starter for the other two outdoorfans of the heat pump, and FIG. 3 is a simplified circuit schematic ofthe electrical components of the heat pump and their controls.

Referring first to FIG. 1, a hermetic, refrigerant compressor C, drivenby an electric motor CM, has its discharge side connected through a tubeto a conventional reversal valve RV. The valve RV is connected by tube11 to one side of indoor air coil 12; is connected by tube 13 to oneside of outdoor air coil .14, and by suction gas tube 16 to the motorCM, through which the suction gas passes to cool the compressor motor asis usual with of a heating relay used 7 ice hermetic compressors. Theother sides of the coils 12 and '14 are connected by a capillary tube 1?serving as a twoway expansion means, in series with a check-valve 18such as is disclosed in the US. Patent 2,785,540 of G. L. Biehn. Thecheck-valve reduces the refrigerant charge during air heating.

One end of the valve RV is connected by a small tube 28 to one end of aconventional pilot valve 19, the other end of which is connected by asmall tube 20 to the other end of the valve RV. The center or" the valve19 is connected by a small tube 21 to the discharge tube 10. The valve19 is adjusted by a solenoid 22 to admit discharge gas into one or theother end of the reversal valve RV for moving a piston therein which isnot shown, to air cooling or air heating positions.

An indoor fan which is not shown, would move indoor air over the indoorair coil 12.

Outdoor air is moved over the outdoor coil 14 by three fans F1, F2 andF3, having electric driving motors FlM, FILM and FSM respectively. Endpartitions 25, and a partition 26 between the fans F1 and F2, direct airfrom the fans over the coil 14. The partition 26 prevents recirculationof air between the fans F1 and F2-F=3 when E1 or F2 and F3 are turnedcit.

Referring now to FIGS. 2a-2f, an outdoor thermostat ODT has a firststage with a normally closed switch ODTSl, and has a second stage with anormally closed SWitCh'ODTSZ and a normally open switch ODTS3. A

cooling relay CR has normally open switches CRSl and CRS2. A heatingrelay HR has normally open switches HRS-1, HRSZ, HRS3 and HRS6, and hasnormally closed switches HR84 and HRSS. A compressor motor starter M81has a normally open switch M818. Fan motor starters M82 and M83 havenormally open switches M828 and M838 respectively.

The switch CRSI is for energizing the compressor motor starter M81 whenthe cooling relay CR is energized, and the switch HRSI is for energizingthe compressor motor starter MS'1 when the heating relay HR isenergized. The switch CRSZ is for connecting the fan motor starters M82and M83 to the supply line L1 when the cooling relay CR is energized,and the switch HR82 is for connecting the fan motor starters M82 and M83to the line L1 when the heating relay HR is energized. The switch ODTSIis for connecting the fan motor starter M82 to the supply line L2 whenthe outdoor temperature is above F, during cooling operation. The switchHRS6 is for connecting the starter M82 to the line L2 when the heatingrelay HR is energized. The switches ODTSZ and HR82 are for connectingthe fan motor starter M83 to the line L2 when the outdoor temperature isabove 60 -F., during cooling operation. The switches ODTS3 and HRSB arefor connecting the fan motor starter M83 to L2 when the outdoortemperature is below 60 1 1, during heating operation, and the switchesODT83 and HRSS are for connecting the starter M83 to the line L2 whenthe outdoor temperature is below 60 F., during cooling operation.

Referring now to FIG. 3, the compressor motor CM is connected throughthe switch M818 to electric supply lines 'L1 and L2. The fan motor FIMis connected through the switch M828 to the supply lines. The fan motorsF-ZM and FSM are connected in parallel, and are connected through theswitch M838 to the supply lines. The cooling relay CR is connectedthrough normally open switch CTS of cooling control thermostat CT to thesupply lines. The heating relay HR, connected in parallel with thesolenoid 22, is connected through normally open switch =HTS of heatingcontrol themostat HT to the supply iines. The compressor motor starterM81 is connected through the switches CR8]. and HRS'I which areconnected in parallel, to the supply lines. The fan motor starter M83 isconnected in one path through the switch ORSCZ shun-ted by the switchHRS2, the switch HRS4 and the switch ODTSiZ, in series to the supplylines, and in another path through the switch CRSZ shunted by the switchH'RSQ, and the switches HRS3 and ODTSS, in series to the supply lines.The fan motor starter M82 is connected in one path through the switchCRS'Z shunted by the switch HRSZ, and the switch ODTSd shunted by theswitch HRS6, in series to the supply lines, and in another path throughthe switch CRSZ shunted by the switch HRSZ, and the switches HRS5 andODTS39, in series, to the supply lines.

Air cooling operation Normally, the reversal valve RV is in its aircooling position. When the thermostat CT calls for cooling, it closesits switch CTS which energizes the cooling relay CR. The relay CR thencloses its switches CR8]. and *CRSZQ The closed switch CRSl energizesthe compressor motor starter M81 which closes its switch M3 13 andenergizes the compressor motor CM. The closed switch ORSZ energizes thefan motor starter M53 through the closed switches HRS4 and ODTS 2, andenergizes the fan motor starter M82 through the closed switch ODTS'l.The fan motor starters MSZ and M83 close their switches MSQS and MSSSrespectively. The closed switch M82 starts the fan motor tFllM. Theclosed switch MSSS starts the tan motors FZM and 1 3M.

Discharge gas from the compressor C passes through the tube 10, thereversal valve RV and the tube 13 into the outdoor coil 14- operating asa condenser. Refrigerant liquid from the coil 14 flows through thecapillary tube 17 and the restrictor valve 118 and is expanded in theindoor coil 12 operating as an evaporator. Suction gas passes from thecoil 12 through the tube-11 1, the reversal valve RV and the tube 16 andcompressor motor OM to the compressor C.

When the outdoor temperature decreases, for example,

below 75 1R, so that the condensing pressure is too low to properlyope-rate the capillary tube 17 as an expansion A means, the switchODTSdof the outdoor thermostat ODT Air heating operation When theheating control thermostat HT calls for heat, it closes its switch HTSwhich energizes the heating relay HR. The relay HR then closes itsswitches HRSll, HRS Z, HRS? and HRS, and opens it switches HRS4 andHRSS. The closed switch HRSl energizes the compressor motor 7 starterMSl which closes its switch MS'IS, starting the compressor motor CM.Assuming that the outdoor temperature is below 60 1F., so that theswitch ODTS'S is closed, the closed switch HTS'2 energizes the fan motorstarter MSS through the now closed switches ODTS3 and I-IRS. The fanmotor starter M82 is energized through the now closed switches H RSZ andHRS6. The starter MSZ closes its switch MSZS, starting the fan motor 11M.

- The starter M83 closes its switch MS3S starting the tan motors PlZMand P 3M.

' The closed switch HTS of the heating thermostat HT also energizes thesolenoid '2-2 which adjusts the pilot valve 1 9 to switch the reversalvalve RV to its air heating position. Discharge gas from the compressorflows through the tube 10, the reversal valve RV and the tube 11 intothe indoor air coil @12 operating as a condensor. Refrigerant liquidfrom the coil 12 flows through the restrictor valve '18 and thecapillary tube 117 and is expanded into the outdoor coil 11-4 operatingas an evaporator. Suction gas flows from the coil '14 through the tube'13, the reversal valve RV and the tube 1'6 and motor CM to thecompressor C.

When the outdoor temperature increases above 60 F., the switch ODTSS ofthe outdoor thermostat ODT opens and deenergizes the fan motor starterMS which opens its switch MSSS stopping the fan motors vFZM and FBM.This prevents excessive compressor head pressure at high outdoorambients.

Thus, a lowambient control and a high ambient control are combined.

, What is claimed is:

In a heat pump having an outdoor air coil, an indoor air co-il, arefrigerant compressor, refrigerant reversal means and two-way expansionmeans connected in a refrigeration circuit, means for adjusting saidreversal means to route refrigerant from said compressor to said outdoorcoil to operate said outdoor coil as a condenser and said indoor coil asan evaporator for air cooling, or to route refrigerant from saidcompressor to said indoor coil to operate said indoor coil as acondenser and said outdoor coil as an evaporator for air heatingoperation, first, second and third fans for moving outdoor air over saidoutdoor coil, said first, second and third fans having first, second andthird electric driving motors respectively, a two-stage outdoorthermostat having a first switch that is closed when the outdoor air isabove a first predetermined temperature, having a second switch that isclosed and a third switch that is open when the outdoor, air is below asecond predetermined temperature lower than said first temperature, acooling control thermostat and a heating control thermostat,thecombination of atcooling relay that is energized when said coolingthermostat calls for cooling, a heating relay that is energized whensaid heating thermostat calls for heating, said cooling relay having aswitch that is closed when said cooling relay is energized, said heatingrelay having first, second and fifth, normally open switches that areclosed, and having third and fourth, normally closed switches that areopened when said heating relay is energized, means including said switchof said cooling relay, said third switch of said heating relay and saidsecond switch of said outdoor thermostat for energizing said second andthird motors, and including said switch of said cooling relay and saidfirst switch of said outdoor thermostat for energizing said first motorwhen the outdoor temperature is above said first temperature and saidcooling relay is energized, means including said switch of said coolingrelay, said fourth switch of said heating relay and said third switch ofsaid outdoor thremostat for energizing said first motor when the outdoortemperature is .below said second temperature and said cooling relay isenergized, and means including said first andise'cond switches of saidheating relay and said third switch of said outdoor thermostat forenergizing said second and third motors when said heating relay isenergized and when the outdoor temperature is below said secondtemperature, and including said first and fifth switches of said heatingrelay for energizing said first motor when said heating relay isenergized, said third switch of said outdoor thermostat opening anddeenergizing said second and third motors when the outdoor temperaturerises above said second temperature while said heating thermostat iscalling for heating.

References Cited by the Examiner UNITED STATES PATENTS WILLIAM J. WYE,Primary Examiner.

